Detail

Object is the base class for all widgets, and for a few non-widget
objects such as Adjustment. Object predates GObject; non-widgets that
derive from Object rather than GObject do so for backward compatibility
reasons.

Object has been removed in Gt3k, but this module still provides useful
functions.

Register a notify callback that is triggered when the given property
has been modified.

Note that this callback is triggered even if the actual value of
the property has not changed.
* Not all attributes are properties. A warning will be generated at
runtime if the passed-in attribute is not a property of the class
with which it was registered.